Advantage of delayed whole-body FDG-PET imaging for tumour detection

Dual-time point positron emission tomography findings of benign mediastinal lymph nodes in a tuberculosis-endemic region

PURPOSE

We performed dual-time-point positron emission tomography imaging (DTPI) in patients without evidence of mediastinal lymph node metastasis to investigate the characteristics of fluorodeoxyglucose (FDG) uptake in benign mediastinal lymph nodes.

MATERIALS AND METHODS

A total of 118 mediastinal lesions in 24 patients were included in the study. The size, attenuation, maximum standardized uptake value (SUV), and retention indices (RI) were recorded on early and delayed positron emission tomography images for lymph node characterization.

RESULTS

The mean SUVs on the early and delayed scans of 118 lymph nodes were 3.3 ± 1.2 and 4.2 ± 1.7, respectively. The mean RI was 26.4% ± 24.5%. Higher FDG uptake was observed in patients with calcified nodules and bilateral FDG uptake and in lymph nodes with calcification or a short-axis diameter >10 mm.

CONCLUSION

In a tuberculosis-endemic area, increments of SUV or RI were frequently observed in benign mediastinal lymph nodes. Therefore, these values, based on mediastinal FDG uptake, might not be accurate indicators of malignant disease.

Clinical significance of primary lesion FDG uptake for choice between oesophagectomy and endoscopic submucosal dissection for resectable oesophageal squamous cell carcinomas

OBJECTIVES

To correlate primary oesophageal squamous cell carcinoma (SCC) (18)F-fluoro-deoxyglucose (FDG) uptake with pathological factors and examine its significance regarding choice of therapy.

METHODS

We retrospectively examined the factors affecting visible and non-visible FDG uptake in 37 primary lesions in 32 oesophageal SCC patients who underwent PET/CT before oesophagectomy or endoscopic submucosal dissection (ESD). We divided the lesions into pathological depth invasion ≥sm2 oesophagectomy (n = 18) and ≤sm1 ESD (n = 19) indicated groups and compared the diagnostic accuracy of FDG-PET with that of endoscopic ultrasound (EUS) performed for 23 superficial lesions to discriminate between these groups.

RESULTS

There were 17 visible and 20 non-visible lesions. The lesion visibility was significantly higher in the larger (≥40 mm), non-flat type, more deeply invaded, positive vascular invasion (P < 0.001 each), positive nodal metastasis (P = 0.04) and higher Glut-1 score (P = 0.005) tumour groups. When the visible and non-visible lesions indicated a need for oesophagectomy and ESD respectively, the sensitivity, specificity and accuracy of oesophagectomy were 94% (17/18), 100% (19/19) and 97% (36/37) and those of EUS were 75% (3/4), 79% (15/19) and 78% (18/23) respectively.

CONCLUSIONS

Primary lesion FDG visibility can be one of the indicators for choosing between oesophagectomy and ESD for resectable oesophageal SCCs.

Clinical usefulness of dual-time FDG PET-CT in assessment of esophageal squamous cell carcinoma

PURPOSE

We conducted this study to investigate the value of the dual-time 2-[(18)F]fluoro-2-deoxy-d-glucose (FDG) positron emission tomography-computed tomography (PET-CT) in assessment of the primary tumor, loco-regional lymph node and distant metastasis in patients with esophageal squamous cell carcinoma.

METHODS

Twenty-six patients with histologically proved esophageal squamous cell carcinoma underwent dual-time FDG PET-CT before radical surgery. The standardized uptake values (SUV(max)) were obtained including early SUV(max) and delayed SUV(max), respectively. The retention index (RI) was also calculated. The results were evaluated retrospectively according to the final pathologic findings. Four diagnostic criteria including (1) early SUV(max)≧ 2.5 alone, (2) RI ≧ 10% alone, (3) a combination of early SUV(max)≧ 2.5 and RI ≧ 10%, and (4) a combination of early SUV(max)≧ 2.5 or RI ≧ 10% were used for differentiating malignancy from a benign lesion, respectively.

RESULTS

The sensitivity of FDG PET-CT in detecting the primary tumor with combination of early SUV(max)≧ 2.5 or RI ≧ 10% was 96.2%. It was statistically significantly higher than the results using the other three criteria (p<0.0001). For loco-regional lymph node detection, there was no significant difference among the 4 criteria. For distal metastases, the significantly higher specificity (100%) was found when using combination of early SUV(max)≧ 2.5 and RI ≧ 10% or using early SUV(max)≧ 2.5 alone than using the other two criteria (p=0.0058). With regard to accuracy, no significant correlations were observed among primary tumor, loco-regional lymph nodes and distant metastasis (p>0.05).

CONCLUSION

The preliminary result of this study demonstrated that dual-time point FDG PET-CT had limited value in detection of primary tumor and loco-regional lymph nodes metastasis. For the distant metastasis, the sensitivity and specificity would be improved if RI ≧ 10% is used as a supplemental criterion. Efforts should be made to improve the ability of the dual-time FDG PET-CT technique to assess primary tumor and loco-regional lymph nodes metastasis.

Searching for alternatives to full kinetic analysis in 18F-FDG PET: an extension of the simplified kinetic analysis method

The most accurate way to estimate the glucose metabolic rate (or its influx constant) from (18)F-FDG PET is to perform a full kinetic analysis (or its simplified Patlak version), requiring dynamic imaging and the knowledge of arterial activity as a function of time. To avoid invasive arterial blood sampling, a simplified kinetic analysis (SKA) has been proposed, based on blood curves measured from a control group. Here, we extend the SKA by allowing for a greater variety of arterial input function (A(t)) curves among patients than in the original SKA and by accounting for unmetabolized (18)F-FDG in the tumor.

METHODS

Ten A(t)s measured in patients were analyzed using a principal-component analysis to derive 2 principal components describing most of the variability of the A(t). The mean distribution volume of (18)F-FDG in tumors for these patients was used to estimate the corresponding quantity in other patients. In subsequent patient studies, the A(t) was described as a linear combination of the 2 principal components, for which the 2 scaling factors were obtained from an early and a late venous sample drawn for the patient. The original and extended SKA (ESKA) were assessed using fifty-seven (18)F-FDG PET scans with various tumor types and locations and using different injection and acquisition protocols, with the K(i) derived from Patlak analysis as a reference.

RESULTS

ESKA improved the accuracy or precision of the input function (area under the blood curve) for all protocols examined. The mean errors (±SD) in K(i) estimates were -12% ± 33% for SKA and -7% ± 22% for ESKA for a 20-s injection protocol with a 55-min postinjection PET scan, 20% ± 42% for SKA and 1% ± 29% for ESKA (P < 0.05) for a 120-s injection protocol with a 55-min postinjection PET scan, and -37% ± 19% for SKA and -4% ± 6% for ESKA (P < 0.05) for a 20-s injection protocol with a 120-min postinjection PET scan. Changes in K(i) between the 2 PET scans in the same patients also tended to be estimated more accurately and more precisely with ESKA than with SKA.

CONCLUSION

ESKA, compared with SKA, significantly improved the accuracy and precision of K(i) estimates in (18)F-FDG PET. ESKA is more robust than SKA with respect to various injection and acquisition protocols.

Diagnostic value of EBUS-TBNA for lung cancer with non-enlarged lymph nodes: a study in a tuberculosis-endemic country

BACKGROUND

In tuberculosis (TB)-endemic areas, contrast-enhanced computed tomography (CT) and positron emission tomography (PET) findings of lung cancer patients with non-enlarged lymph nodes are frequently discrepant. Endobronchial ultrasound-guided transbronchial aspiration (EBUS-TBNA) enables real-time nodal sampling, and thereby improves nodal diagnosis accuracy. This study aimed to compare the accuracy of nodal diagnosis by using EBUS-TBNA, and PET.

METHODS

We studied 43 lung cancer patients with CT-defined non-enlarged mediastinal and hilar lymph nodes and examined 78 lymph nodes using EBUS-TBNA.

RESULTS

The sensitivity, specificity, positive predictive value, and negative predictive value of EBUS-TBNA were 80.6%, 100%, 100%, and 85.7%, respectively. PET had low specificity (18.9%) and a low positive predictive value (44.4%). The diagnostic accuracy of EBUS-TBNA was higher than that of PET (91% vs. 47.4%; p<0.001). Compared to CT-based nodal assessment, PET yielded a positive diagnostic impact in 36.9% nodes, a negative diagnostic impact in 46.2% nodes, and no diagnostic impact in 16.9% nodes. Patients with lymph nodes showing negative PET diagnostic impact had a high incidence of previous pulmonary TB. Multivariate analysis indicated that detection of hilar nodes on PET was an independent predictor of negative diagnostic impact of PET.

CONCLUSION

In a TB-endemic area with a condition of CT-defined non-enlarged lymph node, the negative diagnostic impact of PET limits its clinical usefulness for nodal staging; therefore, EBUS-TBNA, which facilitates direct diagnosis, is preferred.

The sarcoid-lymphoma syndrome

Whether a relationship exists between sarcoidosis and lymphoma is controversial. We present 4 patients diagnosed with sarcoidosis either during or after the treatment of lymphoma, review the data surrounding the entity known as "sarcoid-lymphoma syndrome" and discuss the diagnostic pitfalls it can present. As both entities are fluorine-18 fluorodeoxyglucose avid, histologic verification and clinical acumen are needed to avoid misdiagnosis before initiating therapy.

Effects of blood glucose level on FDG uptake by liver: a FDG-PET/CT study

In FDG-PET for abdominal malignancy, the liver may be assumed as an internal standard for grading abnormal FDG uptake both in early images and in delayed images. However, physiological variables of FDG uptake by the liver, especially the effects of blood glucose level, have not yet been elucidated.

METHODS

FDG-PET studies of 70 patients examined at 50 to 70 min after injection (60 ± 10 min: early images) and of 68 patients examined at 80 to 100 min after injection (90 ± 10 min: delayed images) were analyzed for liver FDG uptake. Patients having lesions in the liver, spleen and pancreas; patients having bulk tumor in other areas; and patients early after chemotherapy or radiotherapy were excluded; also, patients with blood glucose level over 125 mg/dl were excluded.

RESULTS

Mean standardized uptake value (SUV) of the liver, blood glucose level and sex showed no significant differences between early images and delayed images. However, liver SUV in the delayed image showed a larger variation than that in the early image and showed significant correlation to blood glucose level. The partial correlation coefficient between liver SUV and blood glucose level in the delayed image with adjustment for sex and age was 0.73 (P < .0001). Multivariate regression coefficient (95% confidence interval) of blood glucose was 0.017 (0.013-0.021).

CONCLUSION

Blood glucose level is an important factor affecting the normal liver FDG uptake in nondiabetic patients. In the case of higher glucose level, liver FDG uptake is elevated especially in the delayed image. This may be due to the fact that the liver is the key organ responsible for glucose metabolism through gluconeogenesis and glycogen storage.

Analysis of various malignant neoplasms detected by FDG-PET cancer screening program: based on a Japanese Nationwide Survey

OBJECTIVE

The most distinctive feature of FDG-PET cancer screening program is the ability to find various kinds of malignant neoplasms in a single test. The aim of this survey is to clarify the range and frequency of various malignant neoplasms detected by FDG-PET cancer screening performed in Japan.

METHODS

"FDG-PET cancer screening" was defined as FDG-PET or positron emission tomography and computed tomography (PET/CT) scan with or without other tests performed for cancer screening of healthy subjects. This survey was based on a questionnaire regarding FDG-PET cancer screening. We analyzed the situation of 9 less frequently found malignant neoplasms including malignant lymphoma, malignancy of head and neck, esophagus, hepatobiliary and gallbladder, pancreas, kidney, cervical and uterine, ovary, and bladder.

RESULTS

The detailed information of subjects with the suspected 9 kinds of malignant neoplasms mentioned above in the FDG-PET cancer screening program was studied in a total of 1,219 cases from 212 facilities. A statistical significance between PET/CT and PET was found in relative sensitivity and PPV for renal cell cancer. Malignant lymphoma was frequently of indolent type, suspected head and neck cancers had many false-positive results, and pancreatic cancer detected in this program was often in the advanced stage even in asymptomatic subjects. The recommendation of combined screening modality to PET or PET/CT was as follows: gastric endoscopy for assessing early esophageal cancer; abdominal ultrasound for screening hepatobiliary and gallbladder cancer; pelvic magnetic resonance imaging for assessing gynecological and pelvic cancers; and the CA125 blood test for screening ovarian cancer. Delayed image was helpful depending on the type of suspected malignant neoplasm.

CONCLUSION

We analyzed various types of malignant neoplasms detected by the FDG-PET cancer screening program and presented recommended combination of examinations to cover FDG-PET and PET/CT.

Dual phase FDG-PET imaging of brain metastases provides superior assessment of recurrence versus post-treatment necrosis

To study the ability of dual phase FDG-PET/CT imaging to accurately distinguish tumor versus necrosis in patients treated for brain metastases. 32 (22 female, 10 male) consecutive patients with treated brain metastases, lesion size greater than 0.5 cm(3) and suspected recurrence on MRI underwent dual-phase FDG-PET/CT. Clinical outcome was assessed by biopsy or by MRI. SUVmax and SUVmean values of the lesion (L) and gray matter (GM) at the level of the thalamus were measured on early (1) and delayed (2) imaging. L1/GM1 and L2/GM2 and the change of L/GM ratios as a function of time were calculated [(L2/GM2 - L1/GM1)/(L1/GM1)]. Cut-off values were obtained by ROC analysis. P < 0.05 defined statistical significance. Seven patients were excluded due to indeterminate outcomes. 25 patients (16 female, 9 male; 27 lesions; 28 scan sessions) had clear outcomes, proven by either biopsy (n = 16 patients) or serial follow-up MRI (n = 9 patients). Primary subtypes included breast (n = 9), lung (n = 7), melanoma (n = 3), squamous cell cancer of the head and neck (n = 2) and other (n = 4). Twenty-two patients underwent prior radiation (2-113 months) and three received only prior chemotherapy (5 months to 3 years). A change >0.19 of L/GM ratios as a function of time was 95% sensitive, 100% specific, and 96.4% accurate (P = 0.0001; AUC = 0.97) for distinguishing tumor versus radiation necrosis. The ratio of the change of the lesion to WM ratios over time was the second best indicator of outcome when compared to all indices used (ROC cut-off = 0.25, sensitivity 89.5% and specificity 90.9%, and accuracy 89.2%; P = 0.0001; AUC = 0.95), Early or late SUVs of the lesion alone did not differentiate between tumor and necrosis. Regardless of histological type, differentiation of necrosis from metastatic brain lesions was improved by using the change of lesion to gray matter SUVmax ratios as a function of time.

Perioperative (18)F-fluorodeoxyglucose-guided imaging using the becquerel as a quantitative measure for optimizing surgical resection in patients with advanced malignancy

BACKGROUND

(18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography/computed tomography (PET/CT) scanning is a widely accepted preoperative tumor imaging modality. Herein, we evaluate the becquerel (Bq) as a potential novel quantitative PET measure for application of surgical specimen imaging.

METHODS

Retrospectively, PET-avid lesions that could be followed from preoperative imaging, confidently identified in the operating room, imaged ex vivo, and correlated with histopathology were included in this study. Bq counts from both in vivo (preoperative) and ex vivo (surgical specimen) PET/CT images were measured and correlated with histopathology.

RESULTS

Fifty-five PET-avid lesions in 37 patients were included. Forty-six of 55 PET-avid lesions identified were found to contain malignancy on histopathology. Mean Bq counts for the PET-avid lesions were significantly higher that the adjacent PET-nonavid areas (background) within both in vivo and ex vivo imaging (P < .001 and P < .001, respectively). When analyzing all 55 lesions, we found significant increases in Bq levels. PET-avid lesions from in vivo to ex vivo images (P < .001) without significant increases in Bq levels in PET-nonavid lesions from in vivo to ex vivo images (P = .06). When comparing Bq levels between the 2 groups (malignant and benign), we found significantly higher Bq counts in the malignant group on in vivo imaging (P = .02) as well as significantly lower Bq counts in FDG-nonavid areas on ex vivo imaging (P = .04) within the malignant group. Significant differences in PET-avid to PET-nonavid Becquerels ratios within both in vivo and ex vivo images (P = .004, P = .002 respectively) were found, with ex vivo ratio being significantly higher (P < .001).

CONCLUSIONS

(18)F-FDG PET/CT imaging using Bqs is the potential to discern malignant lesions from benign tissues within both in vivo and ex vivo scans.

[18F]Fluorodeoxyglucose-PET/CT differentiation between physiological and pathological accumulations in head and neck

OBJECTIVES

The purposes of this study were to evaluate various physiological fluorodeoxyglucose (FDG) accumulations in the head and neck and to compare those with tumor (pathological) FDG accumulation.

METHODS

One hundred and twelve patients with head and neck carcinomas were studied. PET/computed tomography examinations were performed 1 h after intravenous injection of fluorine-18-labeled FDG. The tumor and the physiological FDG accumulations were identified with PET/computed tomography images, and the maximum of the standardized uptake value (SUVmax) was calculated.

RESULTS

Physiological FDG accumulation was observed in tonsil, extraocular muscle, masticatory muscle, vocal cord, and the major salivary glands: parotid, submandibular, and sublingual gland. The accumulation in tonsil, extraocular muscle, and sublingual gland showed relatively high SUVmax. The tumor FDG accumulation was significantly higher than any physiological FDG accumulation. The optimal cut-off values of SUVmax for differentiating physiological FDG accumulation from pathological FDG accumulation were 4.0 for parotid gland, 4.5 for submandibular gland, 5.5 for sublingual gland, 8.0 for tonsil, and 10.0 for extraocular muscle. The right-to-left ratio of SUVmax was less than 1.5 in any physiological accumulation.

CONCLUSION

Tonsil, extraocular muscle, and sublingual gland showed relatively high FDG accumulation, which was sometimes similar to tumor accumulation. The right-to-left ratio of SUVmax was considered useful in differentiating tumor from physiological accumulation, and the presence of tumor might be highly suspected in cases with a ratio of 1.5 or more.

FDG PET and PET/CT in the Management of Pediatric Lymphoma Patients

Fluorodeoxyglucose (FDG) PET has an ever-increasing role in the management of Hodgkin's and non-Hodgkin's lymphomas, which has been demonstrated in numerous studies in the adult population. In children and adolescents, however, only a limited number of studies have investigated the role of FDG PET in lymphoma. This article reviews the currently available literature on the clinical application of FDG PET in the management of childhood lymphoma. The authors believe that FDG PET (and especially PET/CT) is a valuable imaging modality in the initial diagnosis, response assessment, and post-therapy residual evaluation of Hodgkin's and FDG-avid non-Hodgkin's lymphomas in children and adolescents, and will have a significant impact on the clinical management of pediatric lymphoma.

Schwannoma of the esophagus: a case exhibiting high 18F-fluorodeoxyglucose uptake in positron emission tomography imaging

Esophageal schwannoma is rare and it is difficult preoperatively to confirm a definitive diagnosis, even using current imaging techniques. We present a case of a benign esophageal schwannoma that was surgically excised and confirmed by immunohistochemical staining. Conventional radiological studies, including barium meal, computed tomography and endoscopic examination had shown a solid submucosal tumor of the upper thoracic esophagus but had been unable to confirm the diagnosis. Positron emission tomography was carried out to evaluate the malignant potential and showed a high uptake of 18F-fluorodeoxyglucose (FDG) into the tumor in both the early and delayed phase, suggesting that the tumor was a potentially malignant tumor such as a gastrointestinal stromal tumor. This is the first reported case of esophageal schwannoma that indicated a high FDG uptake. Although consensus has not been reached regarding the precise mechanism of FDG accumulation in schwannomas, we discuss our clinicopathological findings and review other studies of the subject.

Differential diagnosis between (18)F-FDG-avid metastatic lymph nodes in non-small cell lung cancer and benign nodes on dual-time point PET/CT scan

OBJECTIVE

To clarify the difference of (18)F-FDG uptake kinetics between FDG-avid metastatic lymph nodes (LNs) in patients with non-small-cell lung cancer (NSCLC) and FDG-avid benign LNs associated with various etiologies on dual-time point PET/CT scan, and to determine the optimal parameter for differentiation.

METHODS

The subjects were 134 FDG-avid metastatic LNs in 67 patients with NSCLC and 62 FDG-avid benign LNs in 61 patients with various lung disorders including NSCLC. PET/CT scan was performed at 2 time points (at 60 min and at 120 min) after intravenous injection of 4.4 MBq/kg (18)F-FDG. The maximum standardized uptake value (SUVmax) on early and delayed scans and the percent change of SUVmax (%DeltaSUVmax) were measured at each FDG-avid LN. The optimal parameter for differentiation was determined by the receiver-operating characteristic analysis.

RESULTS

Delayed SUVmax was increased compared with early SUVmax in 114 (85.0%) FDG-avid metastatic LNs and 42 (67.7%) FDG-avid benign LNs, with significant higher delayed SUVmax than early values (7.0 +/- 5.0 vs. 5.9 +/- 3.4; P < 0.0001, and 3.0 +/- 1.3 vs. 2.8 +/- 1.0; P < 0.05, respectively). Early and delayed SUVmax and %DeltaSUVmax in metastatic LNs were significantly higher than those in benign LNs (P < 0.0001). The optimal parameter for the differentiation was the combined use of early SUVmax > 3.0 or delayed SUVmax > 4.0, yielding sensitivity of 88.8%, specificity of 80.6%, accuracy of 86.2%, negative predictive value of 76.9%, and positive predictive value of 90.6%. It provided better results than the use of early SUVmax > 3.0 alone (P = 0.019) or the optimal parameter for %DeltaSUVmax (>5%) (P = 0.012). However, 12 (19.3%) benign LNs were indistinguishable from metastatic LNs.

CONCLUSIONS

Although dual-time point PET/CT scan enhances the difference of FDG uptake between FDG-avid metastatic and benign LNs and improves the differentiation when compared with a single scan, biopsy procedure may be still required for accurate assessment of LN status in patients with NSCLC and possible etiologies showing intensive FDG uptake in benign LNs.

Early 2'-deoxy-2'-[18F]fluoro-D-glucose PET metabolic response after corticosteroid therapy to differentiate cancer from sarcoidosis and sarcoid-like lesions

PURPOSE

We aimed at investigating whether early metabolic response to corticosteroid therapy may be used as a diagnostic tool to discriminate between cancer and sarcoidosis, a well-known cause of false-positive 2-deoxy-2-[F-18]fluoro-D: -glucose-positron emission tomography (FDG-PET) findings in oncology.

PROCEDURE

Two cancer patients with biopsy-proven sarcoidosis or sarcoid-like reaction had multiple thoracic FDG foci. After infectious disease had been excluded, patients received oral corticosteroids for 16 and 14 days, respectively, and underwent posttherapeutic FDG-PET examination.

RESULTS

Posttreatment PET revealed a complete metabolic response in both patients, and clinical and imaging follow-up showed no sign of cancer progression.

CONCLUSION

Early metabolic response to systemic corticosteroid treatment may be used as a tool in the establishment of final diagnosis when sarcoidosis is suspected in a cancer patient and could be capable of differentiating cancer from sarcoidosis in the case of coexisting diseases.

Integrated FDG-PET/CT compared with intravenous contrast-enhanced CT for evaluation of metastatic regional lymph nodes in patients with resectable early stage esophageal cancer

OBJECTIVE

To assess whether integrated fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) can improve the diagnostic accuracy of metastatic regional lymph nodes (LNs) in esophageal cancer compared with contrast enhanced CT (CECT).

METHODS

We examined 180 consecutive patients with esophageal cancer by integrated PET/CT between April 2006 and March 2007. Eighteen patients (M:F 14:4) underwent radical esophagectomy after evaluations by PET/CT and CECT of 5-7-mm-thick slices 70-80 s after injection. Regional LNs of esophageal cancer were retrospectively reviewed on CECT images by two blinded evaluators on the basis of the following cutoff sizes: 7 mm for all regional LNs (Protocol A), 10 mm for paratracheal LNs (Protocol B), and 7 mm for others. In addition, the maximum standardized uptake value (SUVmax) on PET/CT was evaluated for positive uptake by LNs.

RESULTS

Of 210 LNs excised at surgery, 25 were positive and 185 were negative for metastasis at pathology. The PET/CT images identified 15 true-positive and 184 true-negative LNs, whereas CECT identified 15 true positives and 176 true negatives in Protocol A, and 14 true positives and 180 true negative in Protocol B. The sensitivity, specificity, accuracy, positive, and negative predictive values of PET/CT were respectively 60.0%, 99.5%, 94.8%, 93.8%, and 94.8%, whereas those of CECT were 60.0%, 95.1%, 91.0%, 62.5%, and 94.6% (Protocol A) and 56.0%, 97.3%, 92.4%, 73.7%, and 94.2% (Protocol B). A comparison of the two CECT protocols revealed fewer false-positive LNs in Protocol B, but slightly lower sensitivity in Protocol B than in Protocol A. Substantial numbers of false-positive LNs were determined by CECT in the paratracheal regions (6 of 9, 66.7%) and CECT revealed central necrosis in 4 of 15 (26.7%) true-positive LNs > 1.8 cm. The mean SUVmax on PET/CT was 2.9 (range 1.7-5.5) in true-positive LNs. The smallest LN metastasis detectable by PET/CT was 6 mm.

CONCLUSIONS

Integrated PET/CT improves the PPV of regional LNs when compared with CECT.

Evaluation of dual-time-point 18F-FDG PET for staging in patients with lung cancer

(18)F-FDG PET is increasingly used for lung cancer; however, some insufficient results have been reported. The purpose of this study was to evaluate the efficacy of dual-time-point (18)F-FDG PET for staging lung cancer and for differentiating metastatic from nonmetastatic lung cancer lesions.

METHODS

One hundred fifty-five lung cancer patients with known or suspected mediastinal and hilar lymph node involvement or distant metastases underwent whole-body (18)F-FDG PET at 2 time points: scan 1 at 60 min (early imaging) and scan 2 at 180 min (delayed imaging) after (18)F-FDG injection. (18)F-FDG PET findings of nodal and distant metastases were evaluated using conventional imaging, clinical follow-up findings, and the results of autopsy or biopsy.

RESULTS

A total of 580 lesions (155 primary lesions, 315 metastatic lesions, and 110 nonmetastatic lesions) were used for analysis. A closer correlation between the primary lesions and metastases was observed for the retention index (RI) standardized uptake value (SUV) than for early and delayed SUV. There was no relationship between the RI SUV results of primary lesions and those of nonmetastatic lesions. The RI SUV of metastatic lesions was approximately 0.5-2 times the RI SUV of primary tumors. We found that the accuracy of (18)F-FDG PET was improved when RI SUV was used for detecting lymph node and distant metastases, because of the significant improvement in specificity relative to early and delayed SUV.

CONCLUSION

RI SUV raised the accuracy for diagnosis of metastases and was superior to early and delayed imaging in terms of differentiating malignancy from nonmetastatic uptake.

Dual-time-point FDG PET for the evaluation of locoregional lymph nodes in thoracic esophageal squamous cell cancer

PURPOSE

Compare dual-time-point and single-time 18F-FDG PET in the evaluation of locoregional lymph node metastases in patients with esophageal squamous cell cancer. Then assess the efficacy of dual-time-point PET in the diagnosis of such nodules.

METHODS

34 patients with thoracic esophageal squamous cell cancer underwent dual-time-point PET before surgery. Semi-quantitative analysis was performed using the standardized uptake value (SUV), obtained from early and delayed images (SUVearly and SUVdelayed, respectively). The retention index (RI) calculated according to the equation: (SUVdelayed-SUVearly) x 100/SUVearly was assessed. Results were compared prospectively in relation to pathologic findings.

RESULTS

71 of 354 resected nodal groups from 28 patients were confirmed positive by pathology. SUVearly of 2.5 and RI of 10 were chosen as arbitrary cutoffs for differentiating malignancy from benign, the sensitivity, specificity, accuracy, negative and positive predictive value of dual-time-point PET were 88.73% (63/71 nodal groups), 91.87% (260/283), 91.24% (323/354), 97.01% (260/268) and 73.25% (63/86) respectively, those of single-time were 76.06% (54/71), 85.16% (241/283), 83.33% (295/354), 93.41% (241/258) and 56.25% (54/96) respectively. P values were 0.047, 0.012, 0.002, 0.052 and 0.017 respectively, indicating remarkable differences in sensitivity, specificity, accuracy, and positive predictive value between dual-time-point and single-time PET.

CONCLUSION

Dual-time-point 18F-FDG PET has the potential for improving the sensitivity, specificity, accuracy and positive predictive value in the evaluation of locoregional lymph nodes in thoracic esophageal squamous cell cancer.

Comparison of early and delayed FDG PET for evaluation of biliary stricture

OBJECTIVE

We assessed whether delayed FDG PET imaging is more useful for the evaluation of biliary stricture in differential diagnosis of malignancy from benign disease.

METHODS

Thirty-seven patients who underwent FDG PET for differential diagnosis of the disease causing biliary stricture were included. FDG PET imaging was performed at 70+/-12 min (early) post FDG injection and repeated 188+/-27 min (delayed) after injection only in the abdominal region. Image analysis was performed with visual interpretation and using a semi-quantitative method if lesion was visible on the PET image. The semi-quantitative analysis using the standardized uptake value (SUV) was determined for both early and delayed images (SUVearly and SUVdelayed, respectively). The tumour-to-normal liver (T/L) ratio was also calculated.

RESULTS

The final diagnosis was cholangiocarcinoma in 29 and benign disease in eight patients. In cases of cholangiocarcinoma, visual analysis of FDG PET using the delayed images, improve the diagnosis with one more patient correctly identified. For early and delayed FDG PET, sensitivities were 82.8% and 86.2%, respectively; specificities were 87.5% for both; and accuracies were 83.8% and 86.5%, respectively. Both SUV and T/L ratio derived from delayed images were significantly higher than those derived from early images for cholangiocarcinoma (P<0.0002 and P<0.0001, respectively).

CONCLUSION

FDG PET could be useful for differential diagnosis of malignancy from benign disease in patients with biliary stricture. Especially, the delayed targeted FDG PET imaging can be recommended in those patients when early imaging is negative or equivalent, because of increased lesion uptake and increased lesion to background contrast ratio.

The role of FDG-PET scans in patients with lymphoma

18-Fluoro-deoxyglucose positron emission tomography (FDG-PET) is a noninvasive, 3-dimensional imaging modality that has become widely used in the management of patients with malignant lymphomas. This technology has been demonstrated to be more sensitive and specific than either (67)gallium scintigraphy or computerized tomography, providing a more accurate distinction between scar or fibrosis and active tumor. PET scans have been evaluated in pretreatment staging, restaging, monitoring during therapy, posttherapy surveillance, assessment of transformation, and, more recently, as a surrogate marker in new drug development. Data to support these various roles require prospective validation. Moreover, caution must be exercised in the interpretation of PET scans because of technical limitations, variability of FDG avidity among the different lymphoma histologic subtypes, and in the large number of etiologies of false-negative and false-positive results. Recent attempts to standardize PET in clinical trials and incorporation of this technology into uniformly adopted response criteria will hopefully lead to improved outcome for patients with lymphoma.

Value of positron emission tomography in staging ocular adnexal lymphomas and evaluating their response to therapy

BACKGROUND AND OBJECTIVE

An observational case series to assess the value of positron emission tomography (PET) in staging ocular adnexal lymphomas and evaluating their response to therapy.

PATIENTS AND METHODS

The clinical records of 16 consecutive patients with ocular adnexal lymphoma for whom pretreatment and posttreatment PET scans and corresponding computed tomography (CT) and magnetic resonance imaging (MRI) scans were available were compared.

RESULTS

Pretreatment PET scans demonstrated fluorine 18-fluorodeoxyglucose (FDG) positive lesions in 15 orbits of 12 patients. In 1 patient with low-grade follicular lymphoma of the orbit, PET revealed an additional focus of lymphoma in the deltoid muscle that was missed on clinical examination and conventional radiography. All of the posttreatment PET scans showed complete resolution of FDG uptake, suggesting good response to therapy. However, posttreatment CT and MRI scans demonstrated residual masses in 3 patients.

CONCLUSIONS

PET is valuable for initial staging of ocular adnexal lymphomas and may be a good adjunct to conventional imaging in evaluation of response to therapy.

Interpretation, accuracy and management implications of FDG PET/CT in cutaneous malignant melanoma

PURPOSE

To investigate the accuracy of different interpretative approaches and to evaluate the management implications of fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) in cutaneous malignant melanoma.

METHODS

We retrospectively identified 60 consecutive patients who underwent 76 PET/CT scans for cutaneous malignant melanoma. PET/CT reports were classified as positive, negative, or equivocal for regional and distant disease. Scan indication (staging, restaging, surveillance, or therapeutic monitoring), tumour stage, presence or absence of regional or distant disease, and post-scan management changes were determined by review of all available medical records. Maximum standardized uptake values (SUV(max)) of all findings were noted. Diagnostic accuracy of PET/CT was compared using either a high or low threshold interpretation (i.e. subtle, but indeterminate findings coded negative or positive, respectively). The frequency of management changes was compared between patient subgroups (stratified by tumour stage or indication).

RESULTS

Using a high threshold interpretative approach, the overall accuracy of PET/CT for disease was 72.4% (55/76), which was significantly (P<0.05) greater than the accuracy of 53.9% (41/76) seen when using a low threshold approach. Per scan accuracy by staging site was 92.1% (70/76) for regional and 76.3% (58/76) for distant disease. PET/CT changed management in 21 of 76 studies (27.6%). When stratified by stage and indication, management changes occurred in all patient subgroups, except for stage I patients (0 of 5).

CONCLUSION

When interpreted with a high threshold approach, PET/CT demonstrates high accuracy for the diagnosis of both regional and distant disease in cutaneous malignant melanoma and frequently changes management in patients with stage II-IV disease referred for a variety of indications.

A case of Lhermitte-Duclos disease presenting high FDG uptake on FDG-PET/CT

Lhermitte-Duclos Disease (LDD) is a rare cerebellar lesion that has long been controversial as to whether the entity is a hamartoma, a malformation, or a neoplasm. Recent advances in metabolic imaging and molecular biology have unveiled biological features of LDD and a close relationship between LDD and Cowden disease. Adult onset LDD is now considered identical to Cowden disease in a US guideline. We present a case of LDD, in which high fluorodeoxy glucose (FDG) uptake was shown on PET/CT. We performed dual time point scans, in which a delayed scan exhibited more intense FDG uptake by the hamartomatous lesion than an early scan. We must remain aware of the possibility of LDD when intense accumulation is observed in a cerebellar lesion on FDG-PET/CT imaging.

FDG PET in oral and oropharyngeal cancer. Value for confirmation of N0 neck and detection of occult metastases

Treatment of the clinical N0 neck in squamous cell carcinoma (SCC) of oral cavity and oropharynx remains a dilemma. None of the current imaging modalities are able to detect the presence of micrometastases in the lymph nodes of clinical N0 necks reliably. The aim of this study was to determine the diagnostic properties of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) in patients clinically staged as N0. FDG PET results of 38 patients were compared to histologic specimens obtained with neck dissections or to follow-up. FDG PET performance was compared to computed tomography (CT), magnetic resonance imaging (MRI) or ultrasonography-guided fine needle aspiration cytology (USgFNAC). Sensitivity and specificity of FDG PET in detecting occult cervical metastases were 50% and 97% respectively. Although FDG PET performed better than conventional imaging modalities, sensitivity was lower than desired. As a consequence, clinical application of FDG PET in the patient staged as N0 is limited.